1. Field of the Invention
The present invention relates to containers in general, and more specifically to stackable containers made of paperboard. In particular, the present invention relates to a ventilated stackable container that is easy to set up, has good structural rigidity, and uses less material in its construction than conventional containers.
2. Prior Art
Containers made of paperboard, i.e., corrugated cardboard, are commonly used in the produce industry to pack, store and ship fresh produce. These containers typically have a bottom, opposite side walls, opposite end walls, and either a closed or an open or partially open top, and when filled with fresh produce are placed on a pallet for shipping and handling. A standard pallet as used in the industry has a width of 40 inches and a length of 48 inches, and the containers are sized so that a plurality of containers can be placed side-by-side on the pallet. A typical container, for example, may have exterior width and length dimensions of about 20 inches by 16 inches, whereby six containers can be placed side-by-side on the pallet. Additional containers are then stacked on top of one another to form multiple layers of containers until a predetermined number of the filled containers are supported in stacked relationship on the pallet.
The loaded pallets may then be transported to a refrigeration unit to cool and/or store the fresh produce. To insure that all of the produce is appropriately cooled, the containers are provided with ventilation openings in at least some of their side, end and/or bottom walls, and are designed so that cooling air can circulate around, through and between the containers stacked on the pallet.
To enable the containers to be stacked on top on one another in stable relationship, stacking tabs are typically provided on the top or bottom edges of at least some of the side and/or end walls, and openings or notches are provided in the opposite edge for receipt of an aligned stacking tab on an adjacent stacked container. In addition to providing a positive detent to prevent lateral shifting of the stacked containers relative to one another, the stacking tabs also serve to index the containers for proper alignment when stacked.
Further, the loaded and stacked containers are subjected to considerable forces during shipment and handling, and must have sufficient structural strength and rigidity to withstand these forces. Thus, the side and/or end walls of the containers are usually constructed with multiple thicknesses, and/or additional reinforcing structure also may be provided, and the flutes of the corrugated material are typically arranged to extend vertically.
Moreover, the containers may be constructed for hand set-up or machine set-up. If intended for hand set-up, they should be easy for the operator to manipulate, and reliably secured in their erected form. In either event, they should be economical to make and use.
U.S. Pat. Nos. 5,485,283 and 5,860,590 are exemplary of prior art stackable containers. Both of them incorporate stacking tabs and at least one wall of double thickness. Additionally, they both have additional reinforcing structure in the comers for added stacking strength. U.S. Pat. No. 5,485,283 has ventilation openings through the side, end and bottom walls, and U.S. Pat. No. 5,869,590 has the opposite end walls inwardly inclined to permit circulation of air between containers arranged in side-by-side abutting relationship. The container in U.S. Pat. No. 5,458,283 utilizes multiple reversely folded panels, and thus consumes a substantial amount of material in its construction. The container in U.S. Pat. No. 5,860,590 requires adhesive to hold it in erected position.
There is need for a paperboard container that is stackable, structurally rigid, easy to set-up, reliably remains in set-up condition, and requires a minimum amount of material in its construction.
A container that meets these needs is disclosed in applicant's copending application Ser. No. 10/287,420. That container is stackable, has structural rigidity, is easy to set-up, reliably remains in set-up condition, and requires a minimum amount of material in its construction. In the particular embodiments disclosed therein, the side walls are of double wall construction, formed by inner and outer roll-over panels, and first flap extensions on opposite ends of the inner roll-over panels are folded inwardly and lie against the inner surface of the end walls. Second flap extensions on opposite ends of the end wall panels are folded inwardly and captured between the inner and outer roll-over panels. The first flap extensions are joined to the ends of the inner roll-over panel by a pair of spaced parallel folds, forming a diagonal panel in each corner of the container. These diagonal panels provide reinforcement and lend substantial stacking strength to the container. First tabs extend upwardly from the upper edge of the outer roll-over panels in spaced relationship along its length, and second tabs on the captured second flap extensions extend upwardly through the upper edge of the side walls and lie against the first tabs to form reinforced double thickness stacking tabs on the upper edge of the side walls. The side walls incorporating the roll-over panels and stacking tabs are inwardly inclined from about 2E to about 4E, whereby when two containers are placed in side-by-side abutting relationship with one another, space is formed between the abutting walls for circulation of cooling air. Notches in the upper edges of the side and end walls, and in some embodiments openings in the field of the walls, provide ventilation for circulation of cooling air through the container and produce held therein.